Known alkali silicate-type inorganic coating compositions are so poor in curability as to form coats low in resistance to boiling water and like properties and exhibit insufficient rust inhibition and corrosion resistance when applied to metallic articles. A highly active curing agent has been used to produce a coating composition with improved curability, thus free from these drawbacks. However, the use of highly active curing agent significantly accelerates curing, thereby shortening the pot life of coating composition to a great extent. Accordingly the use thereof necessitates cumbersome procedures of separately storing a coating composition and a curing agent and mixing them immediately before application of the composition, hence undesirable.
In preparation of gold- or silver-colored or like metallic inorganic coating compositions, metal powder is used to impart a particular metallic luster to a film to be formed. Metal powder, however, when subjected to a high temperature of more than 500.degree. C. is oxidized to become black and devoid of metallic luster. Further, iris-colored inorganic metallic coating compositions with fully satisfactory properties have not been developed heretofore.